Generally, electroluminescence elements are self-luminous, and therefore excellent in visibility. Further, they are perfect solid elements, and therefore have an excellent impact resistance and are easily treatable. Hence, the electroluminescence elements have been expected to be employed as light-emitting elements in various display devices. The electroluminescence elements are classified into (i) inorganic EL elements in which a light-emitting material is an inorganic compound and (ii) organic EL elements in which a light-emitting material is an organic compound. Among these, the organic EL elements can remarkably reduce a voltage to be applied thereto, and therefore have been eagerly studied for practical use.
An organic EL element basically includes an anode, a light emitter layer, and a cathode. The organic EL element can include a hole injecting/transporting layer, and an electron injecting/transporting layer as appropriate. There have been known, for example, (i) an organic EL element including an anode, a hole injecting/transporting layer, a light emitter layer, and a cathode, and (ii) an organic EL element including an anode, a hole injecting/transporting layer, a light emitter layer, an electron injecting/transporting layer, and a cathode. A hole injecting/transporting layer has a function of transmitting, to a light emitter layer, holes injected from an anode. An electron injecting/transporting layer has a function of transmitting, to a light emitter layer, electrons injected from a cathode. There have been known that (i) plural of holes are injected into the light emitter layer in a weaker electric field by sandwiching the hole injecting/transporting layer between the light emitter layer and the anode, and (ii) electrons injected into the light emitter layer from the cathode or from the electron injecting/transporting layer are accumulated on an interface between the hole injecting/transporting layer and the light emitter layer because the hole injecting/transporting layer does not transport the electrons, whereby an emission efficiency is improved. Examples of how to produce a multicolored light emitting element of the organic EL element encompass (1) a color converting method (see, for example, Patent Literatures 1 and 2) for converting blue light into multicolored light of green and red by means of fluorescence conversion, (2) a white light color filtering method (see, for example, non-Patent Literature 1) for converting white light into multicolored light of red, green and blue by use of color filters, and (3) a micro resonator method for producing multicolored light of red, green and blue from white light or various colored light by use of a micro resonator.
Patent Literature 3 discloses a configuration where a light scattering layer, in which metal fine particles are dispersed, is provided between an electrode and a light-emitting layer. The configuration makes it possible to scatter and emit outside light from the light-emitting layer by use of the metal fine particles, thereby improving an emission efficiency. A plasmon phenomenon induced by the metal fine particles makes it possible to utilize light confined in the light-emitting layer or layers in the periphery of the light-emitting layer, whereby light is more efficiently utilized (see Patent Literature 3). Patent Literature 4 discloses a configuration in which plate-like metal particles are arranged in an island manner, and fluorescent molecules are borne therebetween.